What would be a good way to check for a manifold leak on a Milwaukee 8 ?

 

Spray some Gumout carb cleaner on the flanges at each head ( just make sure the engine isn’t super hot, for obvious reasons). If the RPM changes, you’ve got a leak. If it does not affect RPM, it can be assumed there is no leakage.

 

You can also use a propane torch, unlit, and direct the gas at the manifold seals. A change in RPM indicates a leak.